The sizes of produce items such as cherries naturally vary. In addition, the quantities of different sizes can vary depending upon a number of factors such as the site location, the horticultural practices of the grower, and the weather. For example, more larger cherries will typically be produced where the weather for the growing season has been particularly desirable as compared with a growing season having poor weather. In addition, a grower with more desirable horticultural practices, such as proper pruning and fertilizing, will generally produce larger cherries as compared with a grower that does not follow such practices.
Typically, after cherries are harvested they must be sorted into different sizes, since large cherries are much more desirable and command a greater price. In fact, the largest size cherries can command prices up to ten times that of the smallest size cherries. Accordingly, it is extremely important to effectively sort produce items such as cherries according to size. Growers with strict horticultural practices find effective sizing particularly important since a substantial investment is associated with such horticultural practices in order to produce larger cherries. If the cherries are not properly sorted so that larger cherries are sorted into a smaller size grade, this investment is lost. Of course, it is not practically possible to size/measure and sort each and every cherry due to the volume and the extremely large number of individual articles (cherries) that must be handled. Produce items such as cherries are typically sized as they feed over rotating rollers having a diverging gap spacing therebetween, so that smaller cherries are generally removed from the flow stream at smaller portions of the gap and larger cherries are generally removed from the flow stream at larger portions of the gap. This type of sizing/sorting process is an approximation, and each resulting size grouping will have a number of cherries which are larger or smaller than the nominal size range (or grade) for that grouping. However, in sorting cherries, it is important to minimize the amount of smaller cherries which might be grouped with the larger size cherries, since an excessive number of smaller cherries will lead to customer complaints and potential violations of agricultural regulations. For example, in the State of Washington, known for its cherry production, cherries sold as having a specified size must have no greater than 10% of those cherries below the specified size. Many growers/packers also have self-imposed quality standards which exceed agricultural regulations.
It is also important to minimize the number of larger cherries which are grouped with smaller cherries, since the larger cherries can be sold at a greater price. Thus, if larger cherries are sorted into a smaller size grade, a monetary loss is incurred. Accordingly, it is important to sort cherries by size so that a group of cherries of a particular size grade does not contain an excessive amount of cherries above that size or an excessive amount of cherries below that size.
One difficulty in sorting cherries by size is that the diverging roller sorting apparatus removes cherries based upon their minimum dimension. However, from an agricultural product standpoint, cherries are sized by their maximum dimension. In particular, FIG. 1 shows a sizing card 10 which is utilized to determine the particular size of a cherry. If the maximum diameter of the cherry is larger than the diameter of the hole of the card, the cherry will not pass through the hole in the card and attains that size grade. It is of course impractical to size each cherry of a substantial volume of cherries utilizing such a hand held card. Such hand held cards are thus only suitable for a quality control check of selected to samples of cherries or to size a portion of a large volume to gain statistical information concerning that volume.
As is apparent from FIG. 1, certain of the apertures in the sizing card have a numerical designation, e.g., "9 row" or "10 row." These designations originated from very early sizing designations in which cherries were packed in a box of a predetermined size. Cherries of a size in which 9 would fit in a row of the box were thus considered "9 row" cherries, while slightly smaller cherries of a size in which 10 would fit in a row of the box were "10 row" cherries. Thus, a 9 row cherry is larger than a 10 row cherry. Similarly, an 11 row cherry is smaller than a 10 row cherry. The 9 row, 10 row, etc. designations are still widely utilized today, as are intermediate sizes such as 91/2 row, 101/2 row, etc. As shown in FIG. 1, the apertures have designated sizes corresponding to the standard 8, 81/2, 9, 91/2, 10, 101/2, 11, 111/2 and 12 row sizes. As shown in the sizing card, the 8 row cherries have a maximum diameter which is at least 84/64" (33.33 mm), the 81/2 row cherries have a maximum diameter which is at least 79/64" (31.35 mm), the 9 row cherries have a maximum diameter which is at least 75/65" (29.76 mm), 9.5 row cherries have a maximum diameter of at least 71/64" (28.17 mm), 10 row cherries have a maximum diameter of at least 67/64" (26.59 mm), 10.5 row have a maximum diameter of at least 1" (25.4 mm), 11 row have a maximum diameter of at least 61/64" (24.20 mm), 11.5 row have a maximum diameter of at 57/64" (22.62 mm), and 12 row have a maximum diameter of at least 54/64" (21.43 mm). Although not designated on the sizing card of FIG. 1, the cherries having a maximum diameter of at least 52/64" (20.63 mm) are 13 row cherries.
It should be noted that when cherries are sized and packed, each and every one of the possible size grades are not typically utilized. For example, if the crop is good and the amount of very large cherries is high, the largest size of the cherries packed will be 9 row or better cherries (i.e., the cherries are large enough to receive at least a 9 row grade). However, if the amount of 9 row or better cherries is small so as to not be worthwhile packing separately, the largest size cherry will be 9.5 row or better, and the 9.5 row or better product will include not only the 9.5 row cherries, but also cherries large enough to receive a 9 row grade. Thus, a "9.5 or better" product includes cherries which are 9.5 row and larger. Similarly, the second largest product grade of cherries which could be sorted from a crop could be a "10 row or better" product, or a "10.5 row or better" product. The number of size grades into which a given crop are sorted can also vary depending upon customer demand. For example, depending upon customer demand, it might only be necessary to divide cherries into three size groups. In addition, the very large sizes (8 row and 8.5 row) are typically only present in sufficient quantities to pack for certain cherry varieties such as Lapin. Thus, it is to be understood that although a large number of different size grades are known in the industry, as would be understood by those skilled in the art, the cherries of a given crop or group are typically not divided into each and every size grade.
As mentioned earlier, large quantities of cherries have typically been sorted utilizing a diverging roller arrangement as shown in FIG. 2. With this arrangement, a pair of rotating rollers 20, 22 are mounted so that the gap between the rollers is smaller at the upstream end as compared with the downstream end. The rollers are inclined downwardly and rotate so that the cherries are conveyed along the rollers and in the gap between the rollers. As the cherries are conveyed along the rollers, they fall through the gap between the rollers if a dimension of a cherry is smaller than the gap spacing and if that cherry dimension is oriented with respect to the gap to allow the cherry to fall through the gap. Since the rollers diverge, the smaller cherries will generally fall through the gap between the rollers closer to the upstream end of the rollers, while the larger cherries will generally be conveyed further and will fall between the rollers at a location where the gap is larger.
The diverging roller arrangement presents a number of difficulties. First, the diverging rollers do not size cherries according to their maximum dimension (which is the dimension which determines the actual cherry size grade in the industry), but rather according to their minimum dimension. In particular, as the cherries are conveyed along the rollers, they can fall through the gap as long as the dimension of the cherry which is aligned with the gap is small enough. Thus, if the minimum dimension of the cherry "sees" the gap between the rollers, the cherry can fall through the gap and be grouped with a smaller size grade, even though the largest dimension of that cherry will warrant a larger size grading. Thus, the prior art diverging roller arrangement can be wasteful in that larger size cherries can be lost to the smaller grades, since the smaller dimensions of the larger size cherries allows the larger cherries to fall through the gap between the diverging rollers prematurely. The diverging roller arrangement is particularly problematic in that the larger cherries are removed last since the diverging roller arrangement provides the largest gap dimension at the downstream end of the rollers. Accordingly, the larger size cherries are conveyed the greatest distance and have a greater opportunity for their smallest dimension to find the gap between the rollers and fall into a smaller size grade. The loss of larger cherries to smaller size grades is particularly problematic to growers that invest substantial amounts of money in horticultural practices that produce larger cherries.
To reduce the amount of larger cherries which are lost to the smaller size grades, the gap between the diverging rollers can be decreased. However, the amount by which the gap can be decreased is limited, since a decrease in the gap size increases the amount of smaller cherries which will be sorted into lager size grades. As discussed earlier, while the smaller cherries generally fall through the gap sooner (i.e., closer to the upstream end of the diverging rollers) than the larger cherries, a portion of the smaller cherries is conveyed past their actual size so that they fall into a size grading which is larger than their actual size. The smaller cherries can be conveyed to a larger size grade for a number of reasons. In particular, the gap size for a given location at which cherries will be removed for a particular size grade will be smaller than the diameter of the sizing card which corresponds to that grade (i.e., the maximum cherry diameter), to account for the fact that the cherries can fall through the diverging gap when the minimum dimension "sees" the gap. In addition, the cherries typically have stems and can bounce slightly as they are conveyed, which can further allow the cherries to be conveyed downstream past their actual size grade. If the gap between the rollers is narrowed to decrease the amount of larger cherries which are lost to the smaller size grade, a larger number of smaller cherries will travel downstream to larger size grades so that an unacceptably large amount of smaller cherries are present in the larger size grades.
Data concerning minimum cherry dimension vs. maximum dimension (true size) has also revealed that there is no uniform pattern between the minimum dimensions and the true sizes of a group of cherries. As a result, a further difficulty in sizing cherries with the conventional diverging roll arrangement is that the diverging roll tends to size cherries by their minimum dimension and there is no uniform correlation between the minimum dimension, the maximum dimension which can be reliably used to sort cherries according to their maximum size by measuring their minimum size. FIGS. 3(a)-(f) represent the results of an analysis of some 20,000 individual cherries, with the cherries grouped according to their true size (based upon their maximum diameter), and with the graphs for each size group showing the distribution of minimum size dimensions. In particular, FIGS. 3(a)-(e) respectively show the minimum diameter size distribution for each of the 9 row, 10 row, 11 row, 12 row and 13 row true sizes. FIG. 3(f) includes the superposed distributions of FIGS. 3(a)-(e). As is apparent, not only do the cherries of a given maximum dimension (i.e., true size) have a wide range of minimum dimensions, there is also a significant overlap of the minimum dimensions for different maximum dimensions. Particularly notable are the extremely large overlaps of the 9 row with the 10 row and the 10 row with the 11 row. Accordingly, a cherry having a given minimum dimension (the dimension which allows the cherry to go through the smallest gap of a diverging roller sorter) could have a number of different true sizes. The difficulties presented by the overlapping minimum dimensions for different maximum dimensions are noticed in sizing cherries using the conventional diverging roller arrangement. In particular, 10 row cherries are often found in 11 row and 12 row size grades. Similarly, 9 row cherries are often lost to the 10 row and 11 row grades. In view of the foregoing, it is difficult to sort cherries according to their true size utilizing a diverging roller arrangement which tends to size cherries based upon their minimum dimension.
A further shortcoming with the prior art arrangement is that adjustment of the gap (by moving the rollers closer to or farther from one another) results in an adjustment of the gap along the entire length of the rollers. In addition, the conventional diverging roller arrangement simply divides a typical roll length (commonly an 84" roller) into equal segments for each size into which the cherries are being sorted. Thus, if cherries are being sorted into five different sizes, an 84" roller is evenly divided so that approximately 17-18" segments are provided for each size grade. This approach severely constrains the ability to match the gaps of the particular segments to the gap most desirable for a particular size grade, and erroneously assumes that the gap should uniformly increase with each successive size grade. Moreover, since the gaps are all determined by the diverging relationship of the same pair of rollers, adjusting the gap to provide better performance at one region of the rollers can result in a deterioration of the performance at another region of the rollers. For example, if the gap spacing is widened to decrease the amount of smaller cherries which are found in the larger size grades, the gap is widened along the entire length of the rollers and an excessive number of larger cherries can be lost to the smaller size grades. Similarly, if the gap spacing is decreased to decrease the amount of larger cherries which are lost to the smaller size grades, an excessive number of smaller cherries can be conveyed to the larger size grades, resulting in an unacceptable amount of smaller cherries in the larger size gradings.
A still further shortcoming of the prior art is that the gap has been adjusted on a trial and error basis. In particular, if a sorting operation has begun and it is determined that an excessive number of smaller cherries are present in the larger size grades, the gap is increased so that the smaller cherries will drop out earlier, and the amount of the gap increase is essentially a guess. Particularly since the size distributions vary from one group of cherries to another (e.g., groups from different growers), the response to a given gap adjustment has been unpredictable, and such a gap adjustment might correct one sizing problem but result in another sizing problem.
In view of the shortcomings of prior art sizing apparatus and processes and in view of the importance in maximizing the price which cherries can command while maintaining satisfactory quality control, an improved sizing/sorting method and apparatus is needed which can properly sort cherries by size so that an excessive number of larger cherries are not lost to the smaller size grades while an excessive number of smaller cherries are also not sorted into the larger size grades.